Roller-load changing apparatus usable with office machine

ABSTRACT

A roller-load changing apparatus usable with an office machine, such as a facsimile and a convergence machine, includes a document detecting sensor to determine whether a document is stacked, a feed roller to feed the document, a first pinch roller movable between a first pressing position to press the document against the feed roller and a first releasing position to release a pressing force of the first pinch roller, an ejection roller disposed in a downward document feeding direction of the feed roller to eject the document, a second pinch roller movable between a second pressing position to press the document against the ejection roller and a second releasing position to release a pressing force of the second pinch roller, and a roller-load changing unit to change the pressing position of the first and the second pinch rollers when a trailing portion of the document ejects from a nip formed between the feed roller and the first pinch roller

BACKGROUND OF THE INVENTION

1. Field of the Invention

The general inventive concept relates to office machines, such as a convergence machine and a facsimile, and more particularly, to a roller-load changing apparatus for an office machine, capable of preventing a jumping phenomenon of a document from occurring when the document is fed by a feed roller and then is discharged from a nip between the feed roller and a pinch roller supported by a resilient spring urging the document against the feed roller.

2. Description of the Related Art

In general, office machines, e.g., a facsimile, a convergence machine, etc., include a scanning unit for scanning data recorded on a document, and a printer unit for printing the scanned data or other data received via a communication network or input from a computer onto a copy paper.

The scanning unit is an essential component to transmit the data recorded on the document or output the data onto the copy paper.

FIG. 1 shows a conventional scanning unit 10 applied to an office machine, such as a facsimile and a convergence machine. Referring to FIG. 1, the scanning unit 10 includes an automatic document feeder (ADF) 13 located on an upper portion of an interior of the scanning unit for automatically feeding a document D, a scanner 18 for reading data from the document D fed by the ADF 13, a white bar 18′ for bringing the document D into contact with the scanner 18, and an ejection unit 19 for ejecting the document passing through the scanner 18 and the white bar 18′ out of the scanning unit 10.

The ADF 13 feeding the document D into the scanning unit 10 includes a frame 15 providing a document tray with the document D stacked thereon, a first document detecting sensor 1 having a first sensing lever 5 and a first optical sensor 3 for determining whether the document D is stacked, a pick-up roller 14 for picking up the document D according to an operation of the document detecting sensor 1, a friction pad 16 in contact with the pick-up roller 14 for separating the document D into individual sheets by using a friction force, a second document detecting sensor 17 having a second sensing lever 23 and a second optical sensor 21 for sensing when the document is ready to be fed, and a feed roller 14 a for feeding the document D toward the scanner 18 in cooperation with a first pinch roller 14 b having a first shaft 14 d resiliently supported by a first resilient spring 14 c.

Components of the ADF 13 such as the frame 15, the pick-up roller 14, and the feed roller 14 a, may be configured independent of a printing unit (not shown) printing and outputting the data onto the copy paper, as shown in FIG. 1, or may be configured to be commonly used with the printing unit, according to specifications.

The ejection unit 19 includes an ejection roller 19 a for ejecting the document D in cooperation with a second pinch roller 19 b having a second shaft 19 d supported by a second resilient spring 19 c.

According to the conventional scanning unit 10, the feed roller 14 a of the ADF 13 is meshed with the first pinch roller 14 b having the first shaft 14 d supported by the first resilient spring 14 c. When the document D is fed by the feed roller 14 a and then is ejected from a nip between the feed roller 14 a and the first pinch roller 14 b, a resilient force of the first resilient spring 14 c is abruptly removed from the document D, and only a driving force of the feed roller 14 a is applied to the document D. Accordingly, there is a problem of a jumping phenomenon occurring, in which the document D springs out in an advancing direction to above a normal feed pitch (e.g., pitch amount JP of 50 to 60 μm) of the feed roller 14 a at a moment.

Such a jumping phenomenon deteriorates a scan precision of the scanner 18, as shown in FIG. 2. The reason is that since a scan speed of the scanner 18 is set to scan the document D in line with a feed speed of the document, the scanner skips the scan for the document D by the jumped pitch amount JP. As a result, there is a problem of an image defect, in which an image of the document D output by the printer unit is printed at an interval equal to the jumped pitch amount JP.

SUMMARY OF THE INVENTION

Accordingly, the present general inventive concept provides a roller-load changing apparatus usable with an office machine, in which when a paper or a document is fed by a feed roller and then is ejected from a nip between the feed roller and a pinch roller supported by a resilient spring urging the document against the feed roller, a resilient force of the resilient spring acting upon the feed roller is gradually decreased, and a resilient force of a resilient spring acting upon an ejection roller is gradually increased, so as to prevent a jumping phenomenon of the document.

The present general inventive concept also provides a roller-load changing apparatus usable with an office machine, in which when a paper or document is fed by a feed roller and then is ejected from a nip between the feed roller and a pinch roller, a resilient force of the resilient spring acting upon the feed roller is gradually decreased, while a resilient force of a resilient spring acting upon an ejection roller is not varied, so as to prevent a jumping phenomenon of the document.

Additional aspects and advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept.

The foregoing and/or other aspects and advantages of the present general inventive concept are achieved by providing a roller-load changing apparatus usable with an office machine, such as a facsimile, a convergence machine, etc., including a document detecting sensor to determine whether a document is stacked, a feed roller to feed the document, a first pinch roller movable between a first pressing position to press the document against the feed roller and a first release position to release a pressing force of the first pinch roller, an ejection roller disposed in a downward document feeding direction of the feed roller to eject the document, a second pinch roller movable between a second pressing position to press the document against the ejection roller and a second release position to release a pressing force of the second pinch roller, and a roller-load changing unit to change the pressing positions of the first and the second pinch rollers when a trailing portion of the document moves out of a nip formed between the feed roller and the first pinch roller.

During a time duration at which the trailing portion of the document passes through the document detecting sensor until just before the trailing portion of the document ejects from the nip between the feed roller and the first pinch roller, the roller-load changing unit moves the first pinch roller from the first pressing position to the first releasing position and moves the second pinch roller from the second releasing position to the second pressing position. The roller-load changing unit may include a first resilient spring to elastically urge a first shaft of the first pinch roller, a second resilient spring to elastically urge a second shaft of the second pinch roller, a resilient-spring support to resiliently support the first and second resilient springs against the first and second shafts of the first and second pinch rollers, and being movable between a first position where the first resilient spring is compressed and the second resilient spring is decompressed, and a second position where the first resilient spring is decompressed and the second resilient spring is compressed, and an operating unit to operate the resilient-spring support to allow the resilient-spring support to slowly move from the first position to the second position during the time duration at which the trailing portion of the document passes through the document detecting sensor until just before the trailing portion of the document ejects from the nip between the feed roller and the first pinch roller.

The resilient-spring support may include a hinge shaft fixed to a support frame, and a load changing lever having a first end to resiliently support the first resilient spring against the first shaft of the first pinch roller, a second end to resiliently support the second resilient spring against the second shaft of the second pinch roller, and a center portion pivotally supported on the hinge shaft.

The operating unit may include a load control motor installed to the support frame to generate a driving force, a cam disposed in contact with any one of the first and second ends of the load changing lever to slowly move the load changing lever between the first position and the second position, a cam assisting member to cause any one of the first and second ends of the load changing lever to contact the cam when the cam moves the load changing lever to the second position, and a gear train to transmit the driving force of the load control motor to the cam.

The cam may have an elliptical shape.

Alternatively, the cam can be disposed to have an operating range such that when the cam is located in a position to allow the load changing lever to move to the second position, a distance between the load changing lever and the first shaft of the first pinch roller is longer than a free length of the first resilient spring to form a gap between the load changing lever and the first resilient spring or between the first shaft of the first pinch roller and the first resilient spring, and thereby, the first pinch roller does not exert any force onto the feed roller.

The cam assisting member may include a third resilient spring to resiliently support the other of the first and second ends of the load changing lever against a corresponding one of the first and second resilient springs, and a spring support to support the third resilient spring on the support frame. The resilient force of the third resilient spring may be set to be larger than that of the corresponding one of the first and second resilient springs.

Alternatively, the operating unit may further include a position detecting sensor disposed on any one of the first end of the load changing lever, the second end of the load changing lever, and the cam, to control the load control motor. The position detecting sensor may include a sensing boss formed on any one of the first end of the load changing lever, the second end of the load changing lever, and the cam, and an optical sensor disposed at the support frame corresponding to the sensing boss and having a light emitting portion and a light receiving portion.

The foregoing and/or other aspects and advantages of the present general inventive concept may also be achieved by providing a roller-load changing apparatus usable with an office machine, such as a facsimile, a convergence machine, etc., including a document detecting sensor to determine whether a document is stacked, a feed roller disposed in a downward document feeding direction of the document detecting sensor to feed the document, a pinch roller movable between a pressing position to press the document against the feed roller at constant pressure and a releasing position to release the pressure of the pressing position, and a roller-load changing unit to move the pinch roller from the pressing position to the releasing position during a time duration at which a trailing portion of the document passes through the document detecting sensor until just before the trailing portion of the document ejects from a nip formed between the feed roller and the pinch roller.

The roller-load changing unit may include a resilient spring to resiliently support a shaft of the pinch roller, a resilient-spring support to resiliently support the resilient spring against the shaft of the pinch roller, and being movable between a first position where the resilient spring is compressed to press the pinch roller against the feed roller and a second position where the resilient spring is decompressed to release the pinch roller from the feed roller, and an operating unit to operate the resilient-spring support to allow the resilient-spring support to slowly move from the first position to the second position from when the trailing portion of the document passes through the document detecting sensor until just before the trailing portion ejects from the nip between the feed roller and the pinch roller.

The resilient-spring support may include a hinge shaft fixed to a support frame, and a load changing lever having a first end to resiliently support the resilient spring against the shaft of the pinch roller, and a second end pivotally disposed on the hinge shaft.

The operating unit may include a load control motor installed at the support frame to generate a driving force, a cam disposed in contact with the first end of the load changing lever to slowly move the load changing lever between the first position and the second position, and a gear train to transmit the driving force of the load control motor to the cam.

The cam may have an elliptical shape.

Alternatively, the cam can be disposed to have an operating range such that when the cam is in contact with the first end of the load changing lever to allow the load changing lever to move to the second position, a distance between the load changing lever and the first shaft of the first pinch roller is longer than a free length of the resilient spring to form a desired gap, and thereby, the pinch roller does not exert any force onto the feed roller.

Also, the operating unit may further include a position detecting sensor disposed on any one of the cam and the load changing lever to control the load control motor. The position detecting sensor may comprise a sensing boss formed on any one of the cam and the load changing lever, and an optical sensor disposed at the support frame corresponding to the sensing boss and having a light emitting portion and a light receiving portion.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic view of a conventional scanning unit applied to an office machine, such as a convergence machine and a facsimile;

FIG. 2 is a top view of a document depicting a jumping phenomenon of the document occurring in the conventional scanning unit;

FIGS. 3 and 4 are schematic views depicting an operation of a roller-load changing apparatus according to an embodiment of the present general inventive concept, which is applied to a scanning unit of an office machine, such as a convergence machine and a facsimile.;

FIG. 5 is a schematic view depicting a relationship between an operating range of a cam of the roller-load changing apparatus of FIG. 3 and a free length of a first resilient spring; and

FIG. 6 is a schematic view depicting an operation of a roller-load changing apparatus according to another embodiment of the present general inventive concept, which is applied to a scanning unit of an office machine, such as a convergence machine and a facsimile.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures.

FIGS. 3-5 are schematic views depicting an operation of a roller-load changing apparatus 200 according to an embodiment of the present general inventive concept, which is applied to a scanning unit 100 of an office machine such as a convergence machine and a facsimile.

The scanning unit 100 includes an automatic document feeder (ADF) 13 located on an upper portion of an interior of the scanning unit 100 to automatically feed a document D, a scanner 18 to read the data from the document D fed by the ADF 13, a white bar 18′ to bring the document D into contact with the scanner 18, an ejection unit 19 to eject the document D passing through the scanner 18 and the white bar 18′ out of the scanning unit 100, and the roller-load changing apparatus 200 to prevent a jumping phenomenon of the document D.

Components of the scanning unit 100 are similar to those of the scanning unit 10 described and shown in FIG. 1, and so their detailed description will be omitted, except for the roller-load changing apparatus 200.

The roller-load changing apparatus 200 according to the embodiment of FIGS. 3 -5 includes first and second resilient springs 14 c and 19 c, a resilient-spring support 210 to resiliently support the first and second resilient springs 14 c and 19 c against first and second shafts 14 d and 19 d of first and second pinch rollers 14 b and 19 b, and an operating unit 220 to selectively operate the resilient-spring support 210 to allow the first resilient spring 14 c to resiliently press the first shaft 14 d of the first pinch roller 14 b or allow the second resilient spring 19 c to resiliently press the second shaft 19 d of the second pinch roller 19 b.

The resilient-spring support 210 can include a hinge shaft 215 firmly fixed to a support frame (not shown), and a load changing lever 211 having a first end 213 to resiliently support the first resilient spring 14 c against the first shaft 14 d of the first pinch roller 14 b, a second end 214 to resiliently support the second resilient spring 19 c against the second shaft 19 d of the second pinch roller 19 b, and a center portion 216 pivotally supported on the hinge shaft 215.

When the load changing lever 211 pivots about the hinge shaft 215, the load changing lever 211 may be moved to a first load position (FIG. 3) where the first resilient spring 14 c resiliently supporting the first shaft 14 d of the first pinch roller 14 b is compressed to press the first pinch roller 14 b against a feed roller 14 a, and simultaneously, the second resilient spring 19 c resiliently supporting the second shaft 19 d of the second pinch roller 19 b is decompressed to release the second pinch roller 19 b from an ejection roller 19 a, and a second load position (FIG. 4) wherein the first resilient spring 14 c is decompressed to release the first pinch roller 14 b from the feed roller 14 a, and simultaneously, the second resilient spring 19 c is compressed to press the second pinch roller 19 b against the ejection roller 19 a.

The load changing lever 211 is maintained in the first load position shown in FIG. 3 by a cam 221 at an initial operation.

During a time period from a time when a second optical sensor 21 of a second document detecting sensor 17 is turned off by a second sensing lever 23 as a trailing portion of the document D passes through the second document detecting sensor 17 until just before the trailing portion of the document D ejects from a nip formed between the feed roller 14 a and the first pinch roller 14 b, the operating unit 220 operates to allow the load changing lever 211 to slowly move from the first load position to the second load position.

The operating unit 220 can include a load control motor 240 installed at the support frame to generate a driving force, the cam 221 disposed in contact with the first end 213 of the load changing lever 211 to slowly move the load changing lever 211 between the first load position and the second load position, a cam assisting member 250 to bring the first end 213 of the load changing lever 211 into contact with the cam 221 when the cam 221 moves the load changing lever 211 to the second load position shown in FIG. 4, and a gear train 230 to transmit the driving force of the load control motor 240 to the cam 221.

The cam 221 can be of an elliptical shape with first and second semi-circle protruding cam surfaces 222 and 223 protruding in a radial direction.

The cam 221 may move between a vertical position (FIG. 3) where one of the first and second semi-circle protruding cam surfaces 222 and 223 is vertically positioned by the gear train 230 transmitting the driving force of the load control motor 240 to lift the first end 213 of the load changing lever 211 and thus move the load changing lever 211 to the first load position, and a horizontal position (FIG. 4) where one of the first and second semi-circle protruding cam surfaces 222 and 223 is horizontally positioned by the gear train 230 to lower the first end 213 of the load changing lever 211 and thus move the load changing lever 211 to the second load position.

Alternatively, the cam 221 can be disposed to have an operating range R (see FIG. 5) such that when the first and second semi-circle protruding cam surfaces 222 and 223 are located in the horizontal position, a distance between the first end 213 of the load changing lever 211 and the first shaft 14 d of the first pinch roller 14 b may be longer than a free length of the first spring 14 c. Therefore, a gap d1 (see FIG. 5) is formed between the first end 213 of the load changing lever 211 and the first resilient spring 14 c (or between the first shaft 14 d of the first pinch roller 14 b and the first resilient spring 14 c), such that the first pinch roller 14 b does not exert any force onto the feed roller 14 a when the cam 221 is in the horizontal position. Accordingly, the cam 221 is adapted not to exert any load onto the document D at the time at which the document D ejects from the nip between the feed roller 14 a and the first pinch roller 14 b.

The cam assisting member 250 can include a third resilient spring 251 resiliently supporting the second end 214 of the load changing lever 211 against the second resilient spring 19 c, and a spring support 253 to support the third resilient spring 251 on the support frame.

The resilient force of the third resilient spring 251 is set to be larger than that of the second resilient spring 19 c, such that when the cam 221 is in the horizontal position to move the load changing lever 211 to the second load position, as shown in FIG. 4, the first end 213 of the load changing lever 211 is in contact with the cam 221 and the second end 214 of the load changing lever 211 resiliently presses the second resilient spring 19 c at a predetermined resilient force.

The gear train 230 to transmit the driving force of the load control motor 240 to the cam 221 can include a motor gear 235 coaxially provided at a shaft 244 of the load control motor 240, a transmission gear 233 meshed with the motor gear 235, and a cam gear 231 coaxially provided to a shaft 227 of the cam 221 to mesh with the transmission gear 233.

Referring to FIG. 3, when the document D is fed in the state in which the cam 221 is in the vertical position at the initial operation, the first end 213 of the load changing lever 211 is lifted by the cam 221 to compress the first resilient spring 14 c, while the second end 214 of the load changing lever 211 is lowered with respect to the hinge shaft 215 to decompress the second resilient spring 19 c. The first spring 14 c presses the first shaft 14 d of the first pinch roller 14 b against the feed roller 14 a to allow the document D to be moved by the feed roller 14 a, and the resilient spring 19 c allows the second shaft 19 d of the second pinch roller 19 b to be released from the ejection roller 19 a, so that the document D is easily moved by the feed roller 14 a, without being obstructed by the ejection roller 19 a and the second pinch roller 19 b.

In contrast, when the load control motor 240 is operated according to an OFF signal of the second optical sensor 21 of the second document detecting sensor 17, thereby transmitting the driving force of the load control motor 240 to the cam 221 via the motor gear 235, the transmission gear 233, and the cam gear 231 of the gear train 230, as shown in FIG. 4, the cam 221 is rotated to the horizontal position. The first end 213 of the load changing lever 211 is slowly moved downward by the third resilient spring 251 of the cam assisting member 250 and the cam 221 to gradually decompress the first resilient spring 14 c, and the second end 214 of the load changing lever 211 is slowly moved upward with respect to the hinge shaft 215 to gradually compress the second resilient spring 19 c. As a result, the first resilient spring 14 c allows the first shaft 14 d of the first pinch roller 14 b to slowly release from the feed roller 14 a. Therefore, when the trailing portion of the document D is ejected from the nip between the feed roller 14 a and the first pinch roller 14 b, the document D may be moved without receiving a load due to the feed roller 14 a and the first pinch roller 14 b. The second resilient spring 19 c gradually applies a force to the second shaft 19 d of the second pinch roller 19 b to compress the second pinch roller 19 b against the ejection roller 19 a, such that the document D is moved by the ejection roller 19 a and the second pinch roller 19 b.

There is no jumping amount due to a jumping phenomenon of the document when the trailing portion of the document D is ejected from the nip between the feed roller 14 a and the first pinch roller 14 b. If any jumping occurs, the jumping is reduced to a negligible amount that cannot be not visually discerned, for example, 20 μm.

The load control motor 240, the cam 221, and the gear train 230 of the operating unit 220 are adapted to operate with respect to the first end 213 of the load changing lever 211, and the cam assisting member 250 of the operating unit 220 is adapted to operate the second end 214 of the load changing lever 211, as shown in FIGS. 3 and 4. However, the present general inventive concept is not limited to the above arrangement, and an alternate arrangement may be installed.

In order to control a stop time of the load control motor 240 to move the cam 221 to the vertical position or the horizontal position, the operating unit 220 can further include a position detecting sensor 260 disposed on the first end 213 of the load changing lever 211.

The position detecting sensor 260 can include a sensing boss 261 formed on the first end 213 of the load changing lever 211, and a third optical sensor 263 disposed on the support frame corresponding to the sensing boss 261 to be operated by the sensing boss 261 and having a light emitting portion and a light receiving portion.

Referring to FIG. 3, after the load control motor 240 is driven in the state in which the cam 221 is in the horizontal position, as shown in FIG. 4, when the driving force of the load control motor 240 is transmitted to the cam 221 via the gear train 230, and the cam 221 is in the vertical position with respect to the load changing lever 211, the load changing lever 211 is moved from the second load position to the first load position. The sensing boss 261 formed on the first end 213 of the load changing lever 211 is detached from the third optical sensor 263. As a result, the third optical sensor 263 outputs the ON signal to a control unit (not shown), such that the control unit interrupts a power for the load control motor 240 to stop the load control motor 240.

In contrast, referring to FIG. 4, after the load control motor 240 is driven in the state in which the cam 221 is in the vertical position with respect to the load changing lever 211 shown in FIG. 3, when the driving force of the load control motor 240 is transmitted to the cam 221 via the gear train 230 and the cam 221 is in the horizontal position with respect to the load changing lever 211, the load changing lever 211 is moved from the first load position to the second load position. The sensing boss 261 is inserted between the light receiving portion and the light emitting portion of the third optical sensor 263. As a result, the third optical sensor 263 outputs an OFF signal to a control unit (not shown), such that the control unit interrupts a power for the load control motor 240 to stop the load control motor 240.

Although the sensing boss 261 and the third optical sensor 263 of the position detecting sensor 260 are installed at the first end 213 of the load changing lever 211, as described and shown in FIGS. 3-5, they may be installed at another position to determine the stop time of the load control motor 240 at the vertical position and horizontal position of the cam 221, for example, the second end 214 of the load changing lever 211 or cam 221.

Although the stop time of the load control motor 240 is detected by the position detecting sensor 260 installed at the frame and the load changing lever 211, as described and shown in FIGS. 3-5, the stop time of the load control motor 240 can also be determined by detecting a rotary angle or a rotating number of the load control motor 240 required to change the vertical position or the horizontal position of the cam 221.

As described above, according to the roller-load changing apparatus 200 of FIGS. 3-5, when the document D is fed by the feed roller 14 a of the ADF 13 and then is ejected from the nip between the feed roller 14 a and the first pinch roller 14 b, the resilient force of the first resilient spring 14 c acting upon the feed roller 14 a is gradually decreased, and the resilient force of the second resilient spring 19 c acting upon the ejection roller 19 a is gradually increased, thereby preventing the jumping phenomenon of the document D from occurring by abruptly eliminating the resilient force of the first resilient spring 14 c and applying only the driving force of the feed roller 14 a to the document D.

Although the roller-load changing apparatus 200 according to the embodiment of FIGS. 3-5 is applied to the scanning unit of the office machine, such as the convergence machine and the facsimile, the present general inventive concept is not limited thereto. The present general inventive concept may be applied to a feed roller and an ejection roller of a printer unit with the same arrangement and principle to improve a print quality.

Reference is now made to FIGS. 3 and 4 to describe the scanning unit 100 of the office machine to which the roller-load changing apparatus 200 according to the embodiment of FIGS. 3-5 is applied.

First, in order to feed or print the document D, when the document D is stacked on the frame 15 having the document tray, the document D is slid down by its weight to collide with the first sensing lever 5 of the document detecting sensor 1, and thus moves along the first sensing lever 5, thereby turning on the first optical sensor 3 of the first document detecting sensor 1.

When the first optical sensor 3 is turned on, a control unit drives a pick-up roller driving motor (not shown) in one direction to rotate the pick-up roller 14. As a result, the pick-up roller 14 separates the document D into a single sheet by using the frictional force against the friction pad 16, and the document D passes through the second document detecting sensor 17, and is fed to the nip between the feed roller 14 a and the first pinch roller 14 b.

At this time, the second sensing lever 23 of the document detecting sensor 17 is lifted by a leading portion of the document D to turn on the second optical sensor 21. The control unit counts the time the second optical sensor 21 is turned on. After a predetermined lapse of time when the document D reaches the nip between the feed roller 14 a and the first pinch roller 14 b, the pick-up roller driving motor is driven in the other direction to interrupt the driving force from the pick-up roller 14 via a transmission shifting apparatus (not shown) and to transmit the driving force to the feed roller 14a. Alternatively, the control unit stops the pick-up driving motor and drives a separate feed roller driving motor (not shown), such that the feed roller 14 a feeds the document D to the scanner 18.

Then, when the document D passes between the scanner 18 and the white bar 18′ adjacent to the feed roller 14 a, the scanner 18 reads data from the document.

At this time, since the load changing lever 211 is in the first load position where the first resilient spring 14 c is compressed by the cam 221 located in the vertical position with respect to the load changing lever 211, as shown in FIG. 3, and the first shaft 14 d of the first pinch roller 14 b is pressed towards the feed roller 14 a, the document D is fed by the feed roller 14 a and the first pinch roller 14 b only.

Then, when the trailing portion of the document D passes through the second sensing lever 23 of the second document detecting sensor 17, the second sensing lever 23 is inserted between the light emitting portion and the light receiving portion of the second optical sensor 21 to turn off the second optical sensor 21.

When the second optical sensor 21 is OFF, the control unit drives the driving motor of the ejection roller 19 a and drives the load control motor 240 in one direction, for example, a clockwise direction, at a desired speed. The driving force of the load control motor 240 is transmitted to the cam 221 through the motor gear 235, the power transmitting gear 233, and the cam gear 231, such that the cam 221 starts moving from the vertical position as shown in FIG. 3 to the horizontal position as shown in FIG. 4.

As a result, the first end 213 of the load changing lever 211 is slowly moved down by the third resilient spring 251 of the cam assisting member 250 to gradually decompress the first resilient spring 14 c. The second end 214 of the load changing lever 211 is gradually moved up with respect to the hinge shaft 215 to gradually compress the second resilient spring19 c.

Accordingly, the first shaft 14 d of the pinch roller 14 b is gradually decompressed by the first resilient spring 14 c, while the second shaft 19 d of the second pinch roller 19 b is gradually compressed by the second resilient spring 19 c toward the ejection roller 19 a. As a result, a feed-in force to feed the document D is gradually moved toward the ejection roller 19 a.

While the trailing portion of the document D turns off the second optical sensor 21 and passes through the feed roller 14 a and the first pinch roller 14 b, the feed-in force of the feed roller 14 a applied to the trailing portion of the document D and the resilient force of the first resilient spring 14 c are gradually decreased, and then are almost removed at that time where the document ejects from the nip between the feed roller 14 a and the first pinch roller 14 b. As a result, the trailing portion of the document D can pass through the nip between the feed roller 14 a and the first pinch roller 14 b without receiving the load due to the feed roller 14 a and the first pinch roller 14 b.

Accordingly, the present general inventive concept can prevent the jumping phenomenon of the document D from occurring due to abruptly eliminating the resilient force of the first resilient spring 14 c and applying only the driving force of the feed roller 14 a to the document D, as a conventional developing unit 10.

Then, as shown in FIG. 4, if the cam 221 is completely moved to the horizontal position with respect to the load changing lever 211, the sensing boss 261 formed on the first end 213 of the load changing lever 211 is completely inserted between the light emitting portion and the light receiving portion of the third optical sensor 263. As a result, the third optical sensor 263 outputs the OFF signal to the control unit, such that the control unit interrupts the power for the load control motor 240 to stop the load control motor 240.

Accordingly, the load changing lever 211 is completely located at the second load position, and the document D is ejected out of the scanner 18 by the ejection roller 19 a driven by the driving motor and the second pinch roller 19 b, with the scanner 18 reading the data from the document D.

When the printing is completed, the control unit drives the load control motor 240 in the other direction, for example, a counterclockwise direction, at a desired speed to move the load changing lever 211 to the first load position that is the initial operation position. The cam 221 is moved from the horizontal position shown in FIG. 4 to the vertical position shown in FIG. 3 by the gear train 230. Although the load control motor 240 is described to be rotated in the counterclockwise direction, the cam 221 may be moved in a clockwise direction, as the cam 221 moves to the horizontal position, since the cam 221 comprises the first and second semi-circular cam surfaces 222 and 223 symmetrical to each other

As a result, the first end 213 of the load changing lever 211 is slowly moved up by the cam 221 to gradually compress the first resilient spring 14 c. The second end 214 of the load changing lever 211 is gradually moved downward with respect to the hinge shaft 215 to gradually decompress the second resilient spring 19 c.

When the cam 221 is completely moved to the vertical position with respect to the load changing lever 211 and the load changing lever 211 is located in the first load position, the sensing boss 261 formed on the first end 213 of the load changing lever 211 is completely detached from the third optical sensor 263.

As a result, the third sensor 263 outputs an ON signal to the control unit, such that the control unit interrupts the power for the load control motor 240 to stop the load control motor 240, thus placing in standby a scanning operation of a next document D.

FIG. 6 is a schematic view depicting an operation of a roller-load changing apparatus 200′ according to another embodiment of the present general inventive concept, which is applied to a scanning unit 100′ of an office machine such as a convergence machine, a facsimile, and so forth.

Components of the scanning unit 100′ are similar to those of the scanning unit 100 described and shown in FIGS. 3 to 5, the detailed description of which will be omitted herein, except for the roller-load changing apparatus 200′.

The roller-load changing apparatus 200′ according to the embodiment of FIG. 6 includes a first resilient spring 14 c, a resilient-spring support 210′ to support the first resilient spring 14 c against the first shaft 14 d of the first pinch roller 14 b and moving the first resilient spring 14 c between a first load position where the first resilient spring 14 c is compressed to press the first pinch roller 14 b against a feed roller 14 a and a second load position where the resilient spring 14 b is decompressed to release the first pinch roller 14 b from the feed roller 14 a, and an operating unit 220′ to operate the resilient-spring support 210′ such that the resilient-spring support 210′ slowly moves from the first load position to the second load position from a time when the trailing portion of the document D passes through the second document detecting sensor 17 to a time when the document ejects from the nip between the feed roller 14 a and the first pinch roller 14 b.

The resilient-spring support 210′ includes a hinge shaft 215 fixed to a support frame (not shown), and a load changing lever 211′ having a first end 213′ to support the first resilient spring 14 c against the first shaft 14 d of the first pinch roller 14 b and a second end 214′ pivotally supported on the hinge shaft 215.

The operating unit 220′ includes a load control motor 240 installed to the support frame to generate a driving force, a cam 221 disposed in contact with the first end 213′ of the load changing lever 211′ to slowly move the load changing lever 211 between the first load position and the second load position, a gear train 230 to transmit the driving force of the load control motor 240 to the cam 221, and a position detecting sensor 260 disposed on the load changing lever 211′ ( or alternatively, on the cam 221) to control a stop time of the load control motor 240.

The arrangement of the load control motor 240, the cam 221, the gear train 230, and the position detecting sensor 260 of the operating unit 220′ is identical with that of the roller-load changing apparatus 200 of FIGS. 3-5, and so a detailed description thereof will be omitted.

The operation of the scanning unit 100′ of the office machine to which the roller-load changing apparatus 200′ according to the embodiment of FIG. 6 is applied is identical with that of the scanning unit 100 according to the embodiment of FIGS. 3 to 5, except that the load changing lever 211′ decompresses only the first resilient spring 14 c to gradually decrease the compression force of the first resilient spring 14 c acting upon the feed roller 14 a so as to prevent the jumping phenomenon of the document D when the document D ejects from the nip between the feed roller 14 a and the first pinch roller 14 b.

As described above, a roller-load changing apparatus usable with an office machine, when a paper or document is fed by a feed roller and then is discharged from a nip between the feed roller and a pinch roller, a resilient force of a first resilient spring acting upon the feed roller is gradually decreased, and a resilient force of a second resilient spring acting upon the ejection roller is gradually increased, or the resilient force of the second resilient spring acting upon the ejection roller is not varied and the resilient force of the first resilient spring acting upon the feed roller is gradually decreased, so as to prevent a jumping phenomenon of the document.

Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents. 

1. A paper feeding apparatus comprising: a feed roller to feed a document; a pinch roller to exert a force on the feed roller to cause the feed roller to feed the document; and a force controlling unit to adjust the force exerted on the feed roller by the pinch roller as the document is fed.
 2. The paper feeding apparatus as claimed in claim 1, wherein the force controlling unit comprises: a lever elastically connected to the pinch roller to adjust the force exerted on the feed roller by the pinch roller.
 3. The paper feeding apparatus as claimed in claim 2, wherein the force controlling unit further comprises: a cam connected to the lever to raise and lower the lever; and a motor to drive the cam.
 4. The paper feeding apparatus as claimed in claim 1, further comprising: a document detector to detect a position of the document, wherein the force controlling unit controls the force of exerted on the feed roller by the pinch roller according to the position of the document detected by the document detector.
 5. A paper feeding apparatus usable with an image forming apparatus, comprising: a feed roller to feed a document into the image forming apparatus; a first pinch roller to exert a first force on the feed roller to allow the document to pass between the feed roller and the first pinch roller; an ejection roller to discharge the document from the image forming apparatus; a second pinch roller to exert a second force on the ejection roller to allow the document to pass between the ejection roller and the second pinch roller; and a lever elastically connected to the first and second pinch rollers to control the first and second forces.
 6. The paper feeding apparatus as claimed in claim 5, wherein the lever comprises: a first end portion elastically connected to the first pinch roller; a second end portion elastically connected to the second pinch roller; and a center portion about which the first and second end portions pivot, wherein when the first end portion is raised the second end portion is lowered, and when the second end portion is raised the first end portion is lowered.
 7. The paper feeding apparatus as claimed in claim 6, further comprising: an operating unit to raise and lower the first and second end portions of the lever to control the first and second forces.
 8. The paper feeding apparatus as claimed in claim 7, wherein the operating unit comprises: a cam disposed at the first end portion of the lever to lift the first end of the lever; and a motor to drive the cam to lift the first end portion of the lever.
 9. The paper feeding apparatus as claimed in claim 8, wherein the operating unit further comprises: an elastic member disposed at the second end portion of the lever to raise the second end portion to raise the second end portion of the lever and to lower the first end portion of the lever when the cam is not lifting the first end portion of the lever.
 10. The paper feeding apparatus as claimed in claim 5, wherein the lever causes the second force to increase when first force is decreased, and the first force to increase when the second force is decreased.
 11. The paper feeding apparatus as claimed in claim 5, wherein while the feed roller feeds the paper, the first force is gradually decreased and the second force is gradually increased.
 12. The paper feeding apparatus as claimed in claim 5, wherein the first force disappears at a time at which the feed roller finishes feeding the document.
 13. A paper feeding apparatus usable with an image forming apparatus, comprising: a feed roller unit to feed a document into the image forming apparatus; an ejection roller unit to eject the document out of the image forming apparatus; and a roller-load changing unit to adjust operations of the feed roller unit and the ejection roller unit proportionally with respect to a distance at which the document advances through the image forming apparatus.
 14. The paper feeding apparatus as claimed in claim 13, wherein the feed roller unit comprises a feed roller and a first pinch roller movable between a first pressing position to press the document against the feed roller and a first releasing position to release a pressing force of the first pinch roller, and the ejection roller unit comprises an ejection roller and a second pinch roller movable between a second pressing position to press the document against the ejection roller and a second releasing position to release a pressing force of the second pinch roller.
 15. The paper feeding apparatus as claimed in claim 14, wherein the roller load changing unit comprises a load changing lever to increase the pressing force between one of the first pinch roller and the feed roller combination and the second pinch roller and the ejection roller combination, while decreasing the pressing force between the other one of the first pinch roller and the feed roller combination and the second pinch roller and the ejection roller combination.
 16. A method of feeding a document through an office machine comprising: feeding a document into the office machine through a first set of rollers by applying a pressure therebetween; ejecting the document out of the office machine through a second set of rollers by applying a pressure therebetween; and controlling an adjustment of the pressure between the first set of rollers and an adjustment of the pressure between the second set of rollers based on an advancement position within the office machine. 